On vehicles having internal combustion engines, in order to reduce oxides of nitrogen (NOx) in the exhaust, it is known to produce a gaseous mixture of hydrogen, carbon monoxide (referred to hereinafter as syngas), which can be used in a variety of ways, such as in the regeneration of adsorption material in NOx traps. The generation of syngas from engine fuel, engine exhaust and air, for use in regenerating NOx traps is disclosed in copending U.S. patent application Ser. No. 10/243,105, filed Sep. 13, 2002. However, the adsorption material may typically be able to absorb NOx in the exhaust for on the order of 80-100 seconds, and yet be completely regenerated in on the order of 5-10 seconds. Another example of such a system is illustrated in commonly owned copending U.S. patent application Ser. No. 10/309,712, filed Dec. 4, 2002.
A typical syngas generator may comprise a catalytic partial oxidizer (CPO hereinafter) which can reform liquid hydrocarbon fuel. When syngas is required, the CPO must be at or above a certain temperature in order to generate the effective amount of syngas within just a few seconds. To do this, the CPO must remain heated; otherwise, there would be a great challenge for starting up and shutting down a CPO frequently. Startup and shutdown of the CPO requires significant, complex controls, thus increasing the cost of the system. Furthermore, on start-up, the catalyst within the CPO potentially goes through a dangerous oxygen/carbon ratio locally, which could potentially melt or damage the CPO catalyst.
Although a CPO could simply be left in the operating condition, and the syngas discarded, this would result in a significant fuel penalty, causing an impermissibly low overall efficiency of the engine system.